

The previous equations resemble the component expressions presented for \(\vec{S}_{\theta }\)  and \(\vec{S}_z\)  and the interference part reported in [1]}. Note that in this case not only \(\nabla \cdot \left\langle \vec{S}_{\text{trans}} \right\rangle =0 \) , but \(\left\langle \vec{S}_r \right\rangle =0\) ; i.e., we have a zero transversal flux of energy [2]}.
